ci(docs-preview): Refactor workflows (#4262)

**Overview of changes:**
- Runner bumped from Ubuntu 22.04 => 24.04
- Revised inline documentation for maintainers.
- The output of `build-docs.sh` is now grouped in the steps action log, and now hides the noise from pulling the image via `docker run`.
- Removed the separate `tar` steps with ZSTD as there is only a directory to archive with recent changes to this workflow. The `upload` + `download` actions are sufficient.
- The `workflow_run` job has had the PR context restore step extracted to a separate job to minimize noise.
- `actions-netlify` is still effectively the same functionality.
  - `github-token` is no longer configured as it doesn't appear needed with the functions disabled.
  - Opt-out of the GH deployments feature which is not needed.

.github/workflows/scripts/docs/build-docs.sh

@@ -7,8 +7,9 @@ set -ex
 # `build --strict` ensures the build fails when any warnings are omitted.
 docker run \
   --rm \
+  --quiet \
   --user "$(id -u):$(id -g)" \
-  --volume "${PWD}:/docs" \
+  --volume "./:/docs" \
   --name "build-docs" \
   squidfunk/mkdocs-material:9.5 build --strict